Description:
------------
After saving an object in __destruct, __destruct is not called again.

Test script:
---------------
class ClassSave {
	function __destruct(){
		global $test;
		$test = $this;
		echo "Destruct\r\n";
	}
}

echo "1: ";
new ClassSave();
echo "2: ";
$test = null;
unset($test);
echo "End\r\n";

Expected result:
----------------
1: Destruct
2: Destruct
End

Actual result:
--------------
1: Destruct
2: End